Hybrid solar cells are designed to exploit the unique interfacial electronic properties at the organic-inorganic boundary. This class of devices is rooted in nanostructured TiO2 or ZnO integrated with conjugated polymers (P3HT), but is rapidly expanding to include many other organic and inorganic materials including single and polycrystalline silicon (42nd IEEE PV Specialists Conference 2015), for example silicon films on flexible polymer substrates or polymer buffered substrates.
A polymer is a large molecule, or macromolecule, composed of many repeated subunits. Because of their broad range of properties, both synthetic and natural polymers play an essential and ubiquitous role in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. Their consequently large molecular mass relative to small molecule compounds produces unique physical properties, including toughness, viscoelasticity, and a tendency to form glasses and semi-crystalline structures rather than crystals.
Hybrid photovoltaic devices have a potential for not only low-cost by roll-to-roll processing but also for scalable solar power conversion. Recently there has been a growing interest in hybrid solar cells. Hybrid solar cells need, however, increased efficiencies and stability over time before commercialization is feasible. In comparison to the 2.4% of the CdSe-PPV system, silicon photodevices have power conversion efficiencies greater than 20%. It is therefore desirable to leverage the unique electronic and optical properties and functionality afforded by organic and inorganic materials, and those which utilize quantum confined nanostructures to enhance charge transport and fine-tune the spectral sensitivity range (42nd IEEEPV Specialists Conference 2015).
Currently there are three types of hybrid solar cells: 1) polymer-nanoparticle composite, 2) carbon nanotubes, 3) dye-sensitized. Recent progress in materials science, however, now makes possible the production of a fourth, entirely new, hybrid solar cell which combines the benefits of a polymer with crystalline silicon and does so at a temperature that allows for material depositions on inexpensive substrates such as soda-lime glass.
U.S. Patent Application Publication 2009/0297774 (P. Chaudhari et al.) discloses a low temperature silicon deposition technique which allows for fabrication using organic materials as substrates.
U.S. Pat. No. 7,691,731 (Bet and Kar) discloses a low temperature silicon deposition technique on soft polymer substrates for a hybrid organic/inorganic solar cell. The process involves providing an aqueous solution medium including a plurality of semiconductor nanoparticles dispersed therein having a median size less than 10 nm, and applying the solution medium to at least one region of a substrate to be coated. The substrate has a melting or softening point of <200° C. The solution medium is evaporated and the region is laser irradiated for fusing the nanoparticles followed by annealing to obtain a continuous film having a recrystallized microstructure.
According to Bet and Kar, recent advances in physical vapor deposition (PVD) chemical vapor deposition (CVD) techniques and the use of excimer laser annealing (ELA) and solid phase annealing (SPA) have reduced the processing temperatures in thin film microelectronics considerably, thus promoting the use of inexpensive lightweight polymer substrates. However, existing silicon film preparation methods produce amorphous, or randomly aligned microcrystalline or polycrystalline Si films containing high densities of intrinsic microstructural defects which limit the utility of such films for high quality microelectronic applications. Deposition of near-single crystal or single crystal Si films on polymer substrates is a step toward achieving high quality flexible microelectronics. However, the non-crystalline nature of polymer makes it very difficult to employ a number of existing vapor-liquid and solid phase epitaxial growth processes because such processes rely on the crystalline character of the substrates. Secondly, the low melting or softening temperature of polymers makes it impractical to utilize the steady-state directional solidification processes, such as Zone melting recrystallization of Si films on SiO2 using a CW laser, a focused lamp, an electron beam or a graphite strip heater, previously developed for producing single crystal Si films. Usually the thin films formed on amorphous substrates are amorphous or are randomly polycrystalline in the sub-micrometer scale. Therefore, a low temperature process for forming highly crystalline or single crystal layers on temperature sensitive polymeric substrates is needed.
Recently there has also been research to make OLEDs (organic light emitting diodes) and OLETs (organic light emitting transistors) from hybrid organic/inorganic materials. However, the research as far as is known to the applicants of this invention, has not made use of eutectics and buffered, textured, substrates for deposition of the inorganic semiconductor material onto the organic polymer layer.
The above-cited references are incorporated by reference as if set forth fully herein.